AIRS PERFORMANCE DURING SPACECRAFT THERMAL VACUUM (TVAC) TESTING - - PowerPoint PPT Presentation

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AIRS PERFORMANCE DURING SPACECRAFT THERMAL VACUUM (TVAC) TESTING - - PowerPoint PPT Presentation

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AIRS PERFORMANCE DURING SPACECRAFT THERMAL VACUUM (TVAC) TESTING Thomas S. Pagano November 8, 2001 1 11/5/2001 Agenda TVAC Accomplishments and Timeline Performance Results Special Test Results Summary and Conclusions 2

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AIRS PERFORMANCE DURING SPACECRAFT THERMAL VACUUM (TVAC) TESTING Thomas S. Pagano November 8, 2001

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Agenda

  • TVAC Accomplishments and Timeline
  • Performance Results
  • Special Test Results
  • Summary and Conclusions
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TVAC ACCOMPLISHMENTS AND TIMELINE

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TVAC WAS A MAJOR MILESTONE FOR AIRS

  • TRW testing showed no influence from

spacecraft or other instruments

  • AIRS performed extremely well. No instrument

related anomalies detected

  • AIRS runs cooler than expected. This means

better potentially longer mission life.

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THANKS TO THE TVAC TEST TEAM FOR THE LONG HOURS AND EXCELLENT EFFORT

(SPECIAL THANKS TO THE MANY OTHERS WHO CONTRIBUTED BUT WERE NOT ABLE TO MAKE THE PHOTO) Your efforts have allowed us to demonstrate that we can successfully operate the AIRS instrument in orbit and characterize its performance!

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THERMAL VACUUM TESTING AT TRW TOOK ALMOST 47 DAYS

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AIRS TVAC ACCOMPLISHMENTS

  • AIRS instrument and all subsystems performed extremely well
  • Accomplishments include:
  • Earth Shield deployed as commanded
  • Detector dewar vacuum integrity test verified no change from BAE tests
  • Coolers work very efficiently and reliably for long periods of time when left undisturbed.
  • Scanner can be started and operated at a lower temperature
  • Focal plane is fully operational and shows gain ratios equivalent to BAE test data
  • AMA can be commanded to known position and works as expected
  • Spectrometer thermal control can be maintained with high stability
  • Performance sensitivity to thermal state (nominal temp and gradients) characterized
  • The AIRS spectrometer can be maintained at a lower temperature set point
  • AIRS operation procedures work as designed
  • Special Calibration Tests work as designed
  • CONCERNS / LIENS
  • On-orbit outgassing plan and timeline needs to be reviewed to prevent ice formation on

foreoptics

  • Spacecraft initiated time jams cause major disruptions to the normal operation of AIRS.
  • AIRS on-orbit thermal model must be updated based on the new thermal data set
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AIRS INSTRUMENT PERFORMANCE RESULTS

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SPECIAL CALIBRATION TEST SEQUENCES (STS) A KEY ELEMENT OF IN-FLIGHT CAL PLAN

  • Transfer pre-flight calibration to in-orbit configuration
  • Same tests performed pre-flight at TRW and in-orbit
  • Tests are traceable to pre-flight calibration using NIST traceable

sources

  • Check location of spectral response functions
  • Re-establish instrument linear radiometric response
  • Discover and quantify potential new sources of stray light

and noise

  • Stray light in the space viewport
  • Determine orbital dependence of noise
  • Set Radiation Circumvention Levels
  • Correct for launch environmental changes
  • Adjust AMA for AB Balance and Spectral Centering
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TWELVE SPECIAL TEST OBTAIN KEY MEASUREMENTS

Test ID Name Description Measurement Obtained AIRS-C1 Normal Mode / Special Events Establish normal DCR and Lamp operation. Flag data for special events Earth Scene targets of opportunity. Focal Plane Model Geolocation SST Acquisitions AIRS-C2 Guard Test Cycles through A, B and A/B Optimum Gains and acquires data. Radiometric Gains NEdT Spectral FP Model (Parylene) AIRS-C3 Channel Spectra Phase Heat and cool spectrometer by ±1K Phase of Channel Spectra AIRS-C4 AMA Adjust AMA is moved to the desired x (spatial) and y (spectral) position. AB Balance Spectral Adjust AIRS-C5 OBC Cool Blackbody heater is turned off IR Linearity AIRS-C6 Variable Integration Time Integration time is varied on readout while scanning Electronics Linearity AIRS-C7 Space View Noise The scan mirror is stopped and parked at OBCs Noise Behavior (Pops, FPN, etc) Drift Characterization AIRS-C8 Radiation Circumvention Same test as AIRS-C7 but with radiation circumvention turned on. Threshold Levels AIRS-C9 Scan Profile Slow part of scan rotated to OBCs Stray Light Calibrator Centration AIRS-C10 Lamp Operations Each of the three lamps are exercised by user command. VIS Gains, VIS Noise AIRS-C11 Warm Functional Focal Plane Power is Cycled Test Pattern Gain Table Loaded FPA Functionality Data Stream Verification AIRS-C12 Cold Functional Same as AIRS-C11 except performed cold. FPA Functionality

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MANY PATHS USED TO OBTAIN CAL DATA PRE- FLIGHT AND DURING FLIGHT

Executables Files Documents AIRS SPACE- CRAFT

SDDU 2 L0 During Flight

L1A PGE L1A L0 DAAC L1B QA Indicators QA Post Processing QA Reports L1B PGE L1B Testbed SPECIAL TEST S/W Cal_coefs STS Reports L1B_limits Cal_props

Pre-Flight and During Flight

AIRS GSS

Pre- Flight

HTC X-Band Rec SDDU SDDU 2GSS

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C1: NORMAL MODE IMAGERY OF NADIR PANEL LOOKS GOOD

AIRS THERMAL IMAGE* NADIR PANEL TEMPERATURE DCR

  • C1 TEST USED TO EXPEDITE DATA AND INITIATE DCR AND PERIODIC LAMP OPERATIONS
  • TVAC VERIFIED PROPER OPERATION

*Small circles identify places where software displays spectra. Please ignore.

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C1: PREDICTED SATURATION LEVELS COMPUTED BASED ON A/D SATURATION

M1 AND M2 DETECTORS MAY SATURATE PRIOR TO A/D SATURATION

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C2: FIRST OBSERVATIONS OF GAINS IN TVAC SHOWED ICING OF OPTICS

  • ICE GONE AFTER

OUTGASSING

  • REQUIRED ELEVATED

TEMP OPERATION UNTIL ICE DISSIPATED

  • ICE TRANSMISSION

SPECTRUM

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C2: NEDTs COMPARABLE WITH THOSE TAKEN AT BAE SYSTEMS

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C3: EXCELLENT GAIN STABILITY AND FIDELITY ALLOW CHANNEL SPECTRA PHASE DETERMINATION

WORK IN PROGRESS

Oscillations due to channel spectra phase change with optics temperature (appx 3° here)

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C5: OBC FLOAT TEST PROVES ABILITY TO MEASURE ON-ORBIT NONLINEARITY

OBC Temperature

  • vs. Time

Temperature Correction of OBC vs Temperature a2 a1 OBC FLOAT TEST CONFIRMS RADIOMETRIC CALIBRATION COEFFICIENTS ON ORBIT C6: USES VARIABLE INTEGRATION TIME AND ALSO CHECKS NONLINEARITY

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C7: SHOWS MOST DETECTORS HAVE GAUSSIAN NOISE

NO FIXED PATTERN NOISE OBSERVED >25,000 NOISE SAMPLES ACQUIRED NUMBER OF EVENTS > 2, 3, 4 SIGMA COUNTED STARE AT SPACE OR OBC AND COLLECT NOISE SAMPLES

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THRESHOLDS DEFINED TO SELECT A AND B DETECTORS

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C7: SOME SCENE DEPENDENCE OF NENS FOR M1 AND M2

Photon Noise Limited M1, M2 Detector Noise Limited M3, M4 Detector Noise Limited M5-M12 Noise data acquired staring at OBC and SV independently give signal dependence on noise

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SV SUBTACTION TECHNIQUE AFFECTS SCENE CORRELATION ERROR

  • At-launch technique
  • Subtacts median of 8 space views (offset) per scan line from

all footprints in the scan line.

  • A new offset is calculated for each scan line
  • Results in more noise along track than along scan because all

footprints use same space view offset

  • Alternate technique
  • Offset calculated as fit to offset for all scans in the granule
  • All scans share a common space view functional dependence
  • Results in lower noise correlation error for well behaved detectors
  • Expect difficulties when we have DCR or moon in the viewport
  • Increases the noise for channels with higher 1/f noise
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21 One Offset Per Scan Gaussian Noise Channel One Offset Per Scan Non-Gaussian Noise Channel

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22 Fitted Offset for Granule Gaussian Noise Channel Gets Better Fitted Offset for Granule Non-Gaussian Noise Channel Gets Worse

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C8, C9, C10 SPECIAL TESTS RESULTS

  • C8: Radiation Circumvention Test
  • Acquired thresholds for one channel per module
  • Should be adequate to set levels for all channels
  • Requires final setting in orbit in radiation environment
  • C9: Scan Profile Test
  • Rotated scan profile allows us to measure stray light on on-

board calibrators

  • Test run successfully and data show no anomalies
  • C10: Vis/NIR Lamps
  • Lamps worked well. Vis/NIR responses as expected
  • Longer than expected turn on transients require longer wait

time after lamp turn on prior to calibration

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SUMMARY AND CONCLUSIONS

  • The AIRS instrument performed exceptionally well in T/V
  • No problems encountered with AIRS instrument
  • We learned a tremendous amount about the instrument
  • Temperature stability requirements
  • Noise behavior
  • Alignment methods (AMA)
  • Spectral and Radiometric Sensitivity
  • Techniques for characterization of performance in orbit
  • Some test procedures need modification
  • Special Test Procedures will be performed again during

A&E phase and will allow traceability of performance from pre-flight to in-orbit